You can think of a human as having sensors and actuators which is all run by human cognition.

Attention

Process for selecting an object on which to concentrate.

Design implications: make information visible when it needs attending to; avoid cluttering the interface with too much information.

Attention Limitations

• People can be easily distracted
• People are creatures of habit
  • very hard to unlearn processes that are done almost automatically
• people multi-task

Multi-Tasking

• carrying multiple tasks out at the same time
  • real life: driving while listening to music
  • lab: draw circle with left hand while drawing a rectangle with the other
• carrying multiple tasks in rapid sequential order (switching)
  • preparing a meal
  • rapidly switching between computer tasks compared to doing only one task

Perception

Process for capturing information from the environment and processing it. Enables people to perceive entities and objects in the world.

Design implications: all representations of actions, events and data (whether visual, graphical, audio, physical or a combination thereof) should be easily distinguishable by users.

Gestalt Laws of Perception

Gestalt Psychology is an attempt to understand the laws behind the ability to acquire and maintain meaningful perceptions in an apparently chaotic world. It can provide instructional designers with an understanding of "aesthetic perception and cognition". Aesthetic design theory provides an avenue for visual analysis - using the laws and principles of Gestalt Psychology.

Creative thought + Gestalt Laws = Good Design

Proximity

Our eyes and minds see objects as belonging together if they are near each other in space.

Similarity

Our eyes and mind see objects as belonging together if they share a common visual property, such as color, size, shape, brightness or orientation.

Invariance

We respond similarly to the same shape in different sizes and orientations.

Simplicity

We see an object as having some perfect or simple shape because perfection or simplicity is easier to remember.

Closure

If something does not quite close itself, such as a circle, triangle or word, we see it closed anyway.

Focal Point

A point of interest, emphasized or different from the others will draw attention.

Figure and Ground

Eyes tries to interrupt an image in terms of a figure and a background.

Symmetry

Symmetrical elements tend to be interpreted as a unified group.

Continuity

Shortened lines may be automatically extended.

Memory

Process for storing, finding, and accessing knowledge. Enables peo ple to recall and recognize entities, and to determine appropriate actions.

Design implication: do not overload user's memory; leverage recognition over recall when possible.

Short vs. Long term Memory

Short:

• a.k.a Working
• 10 to 30 seconds
• 3-4 items
• 7 +/- 2 chunks of independent information according to studies (Miller's Law)
• limited capacity
• instant recall

Long:

• Active: 2000-3000 words (recall)
• Passive: 10000 words (recognition)
• Slower recall, needs organization

Memory Limitations - Impact on UI design

For short term memory avoid situations where users have to remember more than this. Logical grouping helps.

A meaningful UI element will be easier to remember

• use effective words
• icons can be analogies, but not arbitrary choices
• watch out for cultural differences

People can more easily recognize than recall

• use menus, icons, word completions, look ups

Language

Processes for understanding and communicating through language via reading, writing, speaking and listening.

Design implication: minimize length of speech-based menus; accentuate intonation used in speech-based systems; ensure that font size and type allow for easy reading.

Learning

Process for synthesizing new knowledge and know-how. Involves connecting new information and experiences with existing knowledge.

Design implications: leverage constraints to guide new users to guide new users; encourage exploration by new users.

Higher reasoning

Processes that involve reflective cognition such as problem-solving, planning, reasoning and decision-making.

Design implications: make it easy for users with higher levels of expertise to access additional information and functionality to carry out tasks more efficiently.